1. Technical Field
The present invention relates to an illumination device and a liquid crystal display apparatus, and more specifically, to an illumination device in which a wired board on which a light source member is mounted is stuck to a predetermined sticking surface and a liquid crystal display apparatus.
2. Related Art
In general, an illumination device which outputs light emitted from a light source to a predetermined direction by guiding the light by a light guide member formed of translucent material such as acrylic is known as an illumination device which outputs light emitted from a light emitting diode (hereinafter referred to as “LED”), which corresponds to the light source, to a predetermined direction.
Such illumination device is used as a backlight unit of a side light type in a liquid crystal display apparatus. The backlight unit of the side light type is mainly configured by disposing LEDs on side surfaces of a light guide panel of a flat plate shape, which corresponds to the light guide member, and outputs light emitted from the LEDs and incoming from the side surfaces of the light guide panel through a principal plane as an exit plane in a direction of the thickness of the light guide panel (in the direction of the normal line of the principal plane of the light guide panel). An optical sheet such as a diffuser panel and a prism sheet is disposed on the exit plane of the light guide panel to diffuse light outputted from the light guide panel substantially evenly into a plane.
In the liquid crystal display apparatus, a transmissive liquid crystal panel is disposed on an observer side of the backlight unit, so that light outputted from the backlight unit is modulated by the transmissive liquid crystal panel and is outputted toward the observer, so that display on the liquid crystal display apparatus is achieved.
In the backlight unit as the illumination device as described above, a flexible printed circuit board (hereinafter, referred to as “FPC”) which is a flexible wired board having an LED mounted on a mounting surface thereof is used for the purpose of downsizing and weight reduction, and the FPC is stuck to a predetermined position of the backlight unit via the double-faced adhesive sheet (double-faced tape). A backlight unit having a configuration in which the FPC having the LEDs as the light sources mounted thereon is stuck to a predetermined position with the double-faced tape is disclosed as a surface illumination device in Japanese Unexamined Patent Application Publication No. 2005-294172.
In the backlight unit having the configuration in which the FPC having the LEDs mounted thereon is stuck to the predetermined position with the double-faced tape as disclosed in Japanese Unexamined Patent Application Publication No. 2005-294172, for example, when defects such as uneven luminance, entry of foreign substances, and deformation of a casing caused by displacement of the LEDs are found after having stuck the FPC, it is necessary to perform a rework for repairing the defects by separating the FPC once from the stuck double-faced tape. In this manner, when separating the FPC from the double-faced tape, the FPC, having flexibility, is deformed by a force applied thereto for separation from the double-faced tape. However, since electronic parts such as the LEDs mounted on the FPC have generally no flexibility if the FPC is deformed, an excessive stress is applied to soldered joint portions between terminals of the LEDs and the FPC, whereby separation or cracking occurs at the joint portions.
When the separation or cracking occurs at the joint portions with respect to the terminals of the LEDs, it is obliged to replace the FPC. Even though the cracking does not occur, application of an excessive stress to the terminals of the LEDs should be avoided since it may cause defective illumination of the LEDs.